Supergirl has steadily unveiled more and more of its upcoming Flash crossover, though without perhaps acknowledging how The CW’s Barry Allen ends up on CBS. Now, a new report reveals the mechanism behind our Super teamup, while Grant Gustin teases the possibility of adding Legends of Tomorrow and Arrow into the mix next year.

Entertainment Weekly put forth an extensive report on the March 28 “Worlds Finest” crossover, including the exact method of Barry’s journey to Supergirl’s Earth. Barry has typically needed help to breach both time and dimensional barriers, while his CW will battle with Zoom will see the speedster training with “a tachyon device that causes him to run so fast he literally ends up in an alternate universe.”

We’d bet it’s the one visible on Barry’s chest below:

And while Supergirl will mine plenty of fun from Barry’s cross-universe journey, including an easy, almost flirtatious chemistry with upbeat fellow superhero Kara, Jimmy’s resulting jealousy, Barry’s uncertainty how to handle the imposing Cat Grant, or a Livewire / Silver Banshee chemstry reminiscent of The New Batman Adventures, the real event may have only just begun. In addition to some new photos below, Grant Gustin himself teased the possibility of uniting all of CBS and The CW’s DC heroes next year:

[Adding Arrow and Legends] is in the cards at this point. The whole point of us doing this crossover is setting up the fact that maybe next year we can cross over all of them.

Kara gains a new ally when the lightning-fast superhero The Flash suddenly appears from an alternate universe and helps Kara battle Siobhan, aka Silver Banshee, and Livewire in exchange for her help in finding a way to return him home.

We’ll find out more on the road to March 28, so stay tuned for more “Worlds Finest” details of the big Supergirl-Flash crossover!